Spinning of viscose



kl 2%,, 1950 N. L. cox 2 535345 srmumc; 0F VISCOSE Filed April 26, 1947 I ZNVENTOR.

NGRMAN LOUIS 00X ATTORNEY Patented Dec, 26, 1950 SPINNING OF VISCOSE Norman Louis Cox, Claymont, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application April 26, 1947, Serial No. 744,069

24 Claims.

This invention relates to the regeneration of cellulose from viscose. More particularly, it relates to a new process for manufacturing regenerated cellulose articles such as filaments or films having improved properties.

Although the invention is generally applicable to the preparation of filaments, yarns, films, caps, bands, ribbons, and other structures of regenerated cellulose, it will be discussed with particular reference to the production of viscoserayon yarn.

It is known that the general strength and quality of viscose yarns are improved through reduction of the primary swelling of the gel fibers. The great importance of the gel swelling factor in viscose spinning operations has attained full recognition only in the last few years (see, for example, U. S. 2,347,883 and 2,347,884) It is now recognized that, to constitute a commercially useful viscose rayon process, the viscose composi-. tion and the composition of the sulfuric acid coagulating bath must be so balanced as to permit the production of regenerated cellulose filaments having a gel swelling factor of not more than about 6.5. It has been found that, for a given viscose, yarn properties such as tenacity, elongation, softness, etc., are, as a rule, best when spinning is done at or near the point of minimum gel swelling. It has been found, moreover, that yarn properties are improved through methods designed to reduce the gel swelling factor below the above-mentioned value of 6.5 and that, in general, the greater the reduction, the more marked the improvements. Already proposed methods of reducing the gel swelling factor include the addition to the coagulating bath of zinc sulfate or of ferrous,.manganous, or chromic sulfates (U. S. Patents 2,364,273; 2,347,883; 2,347,884). While these methods represent valuable advances in the art, further improvements in yarn properties are needed.

It is well known that unripened viscoses, i. e., viscoses of salt index of about 7 or higher, are not suitable for spinning by the methods currently used in the industry with normally ripened viscoses, i. e., viscoses of salt index of about to 6 or lower. This is attributed to the high primary gel swelling of yarns from green viscoses, even though the high degree of xanthation of green viscoses (which is reflected in proportionately high salt index values) has been thought desirable on theoretical grounds for viscose spinning. A further problem, then, is to make unripened viscose (the socalled green viscose) amenable to spinning. This is highly desirable since the use of unripened viscose would result in decreasing or eliminating the ripening time now necessary in manufacturing practice. Accordingly, methods for further reducing the gel swelling factor of unripened viscose, and in particular, methods involving further improvements in yarn properties are particularly desirable.

An object of this invention is to provide a process of manufacturing regenerated cellulose filaments having gel swelling values lower than heretofore attainable by methods known to the art and exhibiting considerably improved yarn properties. Another object is to provide a process whereby unripened viscose can be spun in conventional spinning equipment to give yarn of high quality. A further object is to provide a process of manufacturing regenerated cellulose yarn having entirely novel and desirable properties. Yet a further object is the provision of a high-tenacity regenerated cellulose fiber having a non-crenulated surface. Other objects will appear hereinafter.

These objectives are accomplished, in accordance with the invention, by extruding viscose into a sulfuric acid-sodium sulfate coagulating bath containing at least 2% of zinc sulfate, and containing dissolved therein at least 0.2% of a soluble monoamine. The said amine is one having at least four carbon atoms but containing a total of no more than ten carbon atoms, no single group being more than six carbon atoms in length. After coagulation, the filaments are stretched, preferably in a secondary bath.

Another object, which was unexpectedly found possible to accomplish through the invention described below, was the production of very highstrength yarns having smooth (non-crenulated) surfaces with improved soil resistance and abrasion resistance. The combination of high tenacity and high fatigue resistance with smooth surface had not heretofore been achieved.

The use, in very low concentrations of certain secondary and tertiary amines in spinning baths or in viscose for preventing or reducing incrustation of spinnerets is known (Br. 533,309). However, the solubility of the agents disclosed in typical spinning baths is much too low to cause a detectable reduction in gel swelling and, accordingly, these agents have been found to be inoperable in this invention. There was, therefore, no reason to expect that certain bath-soluble amines when used above a critical minimum concentration in conjunction with a critical minimum concentration of zinc sulfate in the coagulating bath would have any effect whatever on viscose spinning and/or yarn properties, and even less reason to expect that their use would decrease the gel swelling of the yarn and permit the production, from either ripened or unripened viscose, of high-tenacity filaments possessing some entirely new properties.

By the term bath-soluble monoamine modifiers" is meant those monoamines the organic groups of which total from four to ten carbon atoms, no single group within the molecule having more than six carbon atoms and the solubility of which is at least 0,2%, on a weight basis, in an aqueous sulfuric acid spinning bath containing at least 2% of zinc sulfate and 13% or more of sodium sulfate.

Referring to the drawings:

Figure l is a dyed cross-section of a filament regenerated from unripened, unmodified viscose, and

Figure 2 is a dyed cross-section of a filament, regenerated from viscose unripened, but modified with the agents of and by the processes of this invention.

The invention will be more clearly understood by referring to the examples and discussion which follow. These examples are given for illustrative purposes and are not to be construed in any sense as limitative. The numerical values of gel swelling given below for various yarn samples were all determined according to the following procedure:

The gel thread is collected in a monolayer on a bobbin, by manually operating a traverse mechanism with the thread being stretched 80% in the hot dip bath. The sample is centrifuged (1400 R. P. M.) for a minute, cut off, and weighed in a closed bottle. The sample is washed free of acid, dried in an oven at 105 C., and weighed. The ratio of gel weight to cellulose weight (gramsof gel per gram of cellulose) is referred to as the gel swelling. Variations may be introduced in the procedure, e. g., in the stretch, spinning speed, or length of bath travel, but these introduce only minor changes in the numerical values of gel swelling. In the case of films, excess bath is removed by blotting with pulp sheet and the gel swelling value is expressed as for filaments.

Another important indication of yarn quality is the factor referred to below as "D value. This factor relates to the rate of neutralization of the viscose filament in the coagulating and regenerating bath. It is determined by adding to the viscose a suitable indicator, in this case bromocresol purple (pH range 5.2-6.8), and observing the distance in inches from the spinneret at which the purple color completely disappears in the traveling filament. This distance is the D value. The selected amines suitable for use in this invention reduce the rate of neutralization of the spinning filaments, and, hence, increase the "D" value over that of unmodified viscose. It has been found that, in general, the greater the D value, the better the yarn properties. The increased D value is believed to indicate that the modifying agents of this invention permit greater dehydration of the viscose before the gel structure of the filament is permanently set.

In all the examples, the caustic content of 6% refers to the total alkalinity'expressed as sodium hydroxide. It includes free sodium hydroxide and that combined in the form of sodium carbonate, sodium trithiocarbonate, and sodium cellulose xanthate. The coagulating baths used in the examples, unless otherwise sp cified, were 8 --23-4 baths, or baths containing 8.5% of sulfuric acids, 23% sodium sulfate and 4% zinc sulfate.

4 EXAMPLEI Viscose was prepared in the following manner, using 7% cellulose and 6% total sodium hydroxide (7-6 viscose). Alkali cellulose, aged to get the desired viscose viscosity (40-60 poises) is xanthated for 2 hours using 35% carbon disulfide (based on the recoverable bone-dry cellulose). After mixing 1%; hours at 0 C., the freshly prepared viscose is filtered while it is cold, deaerated, and kept at 0 C. until spun, i. e., it is spun in the unripened state and has a high salt index value, high xanthate sulfur content, and low sodium trithiocarbonate concentration.

The viscose is spun into 275 denier-100 filament yarn by extruding through a spinneret having holes of 0.0025" diameter into primary coagulating and regenerating baths comprising 8.5% H2804, 23% Na2SO4, and4% 211504, and 0.0, 0.2, and 0.4% of triethylamine, respectively. The

apparatus and general procedure used to lead viscose into the bath and to collect the formed thread are essentially the same as those used commercially in the so-called bobbin or spool process. The yarn is given a primary bath travel of 28" by using a roller guide. The specific conditions include a bath temperature of 50 C. and first feed-wheel speed of 485 inches per minute. The filaments are carried through a water bath at 95-100 C. and wound up at such a speed as to give stretch beyond the feed wheel. The resulting regenerated gel yarn is washed free of acid and salt and then processed. The yarns which are dried on the bobbin or, alternately, partially relaxed before drying by rewinding on another bobbin, are twisted four turns per inch and tested after conditioning at 21 C. and 60% relative humidity for 48 hours.

The properties of the yarn prepared from the viscoses described herein are listed in the accompanying table:

Table I Per Cent Triethyla Inc in Bath Properties ing "D" value, in

It will be seen that the gel swelling value is lowest and the D" value highest for the modified baths. The physical properties, especially wet tenacity, are higher than those obtained using the unmodified bath.

The yarn produced by this and other examples has a number of properties which distinguish it sharply from other regenerated cellulose yarn. Its properties are similar to those produced through modification of viscose with short-chain quaternary ammonium compounds which are described and claimed in copending application Serial No. 716,415. The most readily apparent modifications are the new cross-section and surface features. For conventional yarns prepared from viscose spun into zinc baths, a skin or outer shell which swells to a different extent in water than that of the core is visible. These yarn crosssections show both deep and shallow crenulations around the periphery of the filament. However, for yarns spun into zinc baths containing the amine modifiers of this invention, the boundary between the skin and core is very diffuse and crenulations are absent, giving the yarn a smooth surface.

The fact that the filaments of the invention have smooth surface and considerably lower sec 7 ondary swelling (water take-up by dried yarns) results in more resistance to flbrillating, laundering, fatiguing, and soiling action than exhibited by normal crenulated viscose yarns.

EXAMPLE II A 7-6 viscose is prepared and spun in the unripened state in the manner described in Example I. In this case, yarns were collected in separate coagulating baths containing 0.0, 0.2, and 0.4% dibutylamine, respectively. In addition, the yarns were partially relaxed before drying on the bobbin. The yarn properties are tabulated below for both control and modified conditions. It will be noted that the use. of the amine modifier in the coagulating bath gives lower gel swelling, lower rate of neutralization (higher "D value), and improved yarn prop-f erties. I

Table II Percent Dibutylamine in B Properties 3. 58 3. 61 3.87 2. 26 2. 68 2. 78 Ten. g./d., loop. 2. 82 2. 88 3.02 Elong., percent dry 12. 0 13.2 13. 3 Elong., percent Wet.. 20. 4 21. 7 21. 6 Elong., percent loop. 9. 2 10. 3 10. 2 Gel swelling 3. 3 2. 6 2. 6 "D" value, in 2. 7 5.0 6.0

EXAIWPLE III A cotton linters viscose containing 7% cellulose and 6% caustic is prepared and spun as described in Example I. In this case, however, the modifier added to the bath is cyclohexylamine. Yarns with smooth surface and improved properties are obtained by adding 0.3 and 0.5% of this modifier to the bath:

An unripened 7-6 viscose is spun into separate baths containing 0.0 and 0.5% amylamine, re-' spectively, and the yarn is stretched and processed as in Example I. The reduction in gel swelling and neutralization rates (increased D value) and improved yarn properties of the npnbination of an amine (containing no more than 6 crenulated fiber thus obtained are shown in the table below:

Table IV Per Cent Amylamine in Bath Ten. g./d., dry 3. 98 4. 20 Ten. g./d., wet 2.46 2.82 Ten. g./d., loop 2. 72 2. 70 Elong., per cent dry.. 6.5 6.3 Elong., per cent wet 20.0 22.8 Elong., r cent loop 3. 9 3. 5 Gel swe ling 3. 3 2. 6 "D" value, in 2.7 4.5

EXAIWPLE V A cotton linters viscose containing 7% cellulose and 6% total caustic is prepared and ripened to a salt index of 5.0, as is normally done in com mercial production, and then spun into filaments using all the conditions of Example I for collection and processing. In this case, however, the modifier used in the coagulating bath is 0.3% butylmonoethanolamine. Considerable decrease in gel swelling and increase in "D value are obtained, which are reflected in a measurable increase in physical properties of the yarn (see table below). The character of the filament is changed in the same manner as noted with unripened viscose.

EXAMPLE VI A cotton linters viscose containing 7% cellulose and 6% caustic is prepared as in Example I and ripened as described in Example V. A layer of this viscose 0.015 inch thick is spread on a glass plate and then immersed in a coagulating bath at 50 C. Baths containing 6% sulfuric acid, 23% sodium sulfate, and 1, 3, and 4% zinc sulfate, respectively, were used. The following modifiers were added to the coagulating baths: amylamine, cyclohexylamine, dibutylamine, triethylamine, and tributylamine. It will be observed in the table below that these modifiers, even in concentrations as high as 1% in the coagulating bath, have no efiect on gel swelling when only 1% of zinc sulfate is present. As the zinc sulfate concentration is raised, the gel swelling reduction becomes more pronounced and at a 4% zinc sulfate concentration less modifier than in 3% zinc sulfate baths is required to give a specific amount of change in gel swelling value. Tributylamine is sparingly soluble and it will be noted in the table that no appreciable reduction in swelling was obtained with it as modifier, even in the presence of 4% zinc sulfate. The same relationship holds" true in the case of the preparation of fibers. In order to obtain a significant reduction of gel swelling, there must be present the critical comten carbon atoms) soluble in the bath to at least 0.2% and an amount of ZnSO4, at least 2%.

tion during the short'time the filament is in contact with the coagulating bath. Determination The modifying agents suitable for the purpose of this invention are primary, secondary, and tertiary monoamines which are soluble in the coagulating bath to at least 0.2%. It should be noted in this connection that many amines are practically completely insoluble in the normal coagulating baths, e. g., baths containing 13% or more of sodium sulfate, in spite of the fact that the baths are acidic. This is true in particular of the long-chain amines, and even of relatively short-chain amines such as triamylamine, which is not soluble in such coagulating baths even to the extent of 0.2%. Tributylamine is soluble to 0.2% in coagulating baths but 0.5% will not dissolve. If the amine has the solubility requirement, it must also fulfill the following additional conditions previously stated, namely:

(a) It must be a monoamine. It has been found that certain diamines, e. g., ethylenediamine, have practically no effect as regards decrease in gel swelling and increase in D" value.

b) It must have at least four carbon atoms. Lower amines such as methylamine or ethylamine are substantially ineffective.

(c) It must have no more than carbon atoms with no radical of more than six carbon atoms. Larger radicals and high total molecular weight, in addition to decreasing the solubility of the amine, tend to produce surface activity which is not desirable in the process of this invention.

The preferred modifiers are those in which the amino nitrogen is attached to hydrocarbon groups, preferably alkyl groups, and/or to hydroxyalkyl groups. Suitable agents which may be mentioned in addition to those used in the examples are diethylamine, dipropylamine, butylamine, ethyldiethanolamine, pyridine, piperidine, aniline, triethanolamine, dipropanolamine, propylpropanolamine, hexanolamine, amyldiethanolamine, butylmethylethanolamine, propylethanolamine, cyclohexylethanolamine, and hexyldiethanolamine.

The amine modifiers for effective results should be used in the coagulating bath in concentrations of at least 0.2%, based on the weight of the bath, and, in general, it is unnecessary to use more than 1.0% of agent, a generally useful range being 0.20.5%. The optimum concentration of any given agent depends on its eflectiveness and on its molecular weight. For example. larger concentrations of amylamine are needed than for triethylamine. It also depends to some extent on process variables such as the spinning speed, since at the high spinning speeds used in industrial practice less agent is desired than at lower speeds, for the reason that the rate of neutralization of the filament should be retarded only to the extent compatible with complete coagulathose skilled in the art.

The viscose used in the process of the invention may be of a variety of types; for example, it may be from wood pulp, cotton linters, mixtures of the two, or even other types of cellulose. The composition of the viscose may also be varied widely. For example, it may have a cellulose content of from 4 to 10%, or even more, and an alkali content of from 4 to 8% or more. The standard viscoses of the industry, 1. e., those having between 5 and 7% cellulose and between 4 and 6% alkali, are preferably used. The amount of carbon disulfide used in xanthation can be from 25-50% (based on the recoverable bone-dry cellulose). It has been found that higher than normal xanthate sulfur contents (higher salt indices) can be used in the viscose when the amines described herein are added and there appears to be an advantage in stretchability and level of yarn properties if salt indices higher than 5 are used. It is necessary to use 30% or greater amounts of carbon disulfide to obtain salt indices of 5 or over in unripened viscoses. Thus, one of the chief advantages of the invention is that unripened or partially ripened viscoses may be used, with the result that the ripening time and space now required in viscose plants may be eliminated or substantially reduced.

While the use of unripened viscose is of special interest in the process of this invention, it has been shown (Example VI) that notable improvements in yarn quality are also obtained with normally ripened viscose, thus making the process directly applicable to existing plant practice.

The spinning baths suitable for use in the invention contain sulfuric acid, sodium sulfate, and zinc sulfate. Zinc sulfate is an essential component of the spinning bath since, in its absence, or if it is present in insufficient amount, the amine compounds have no effect on spinning and yarn properties. If desired, additional salts of divalent metals known to reinforce or supplement the action of zinc sulfate may be used, such as ferrous sulfate, manganese sulfate, magnesium sulfate, nickel sulfate, or chromic sulfate, particularly the first-named salt. When one or any of these supplementary metal salts are used, smaller amounts of zinc sulfate are required. Preferably, the spinning bath contains from 4 to 12% of sulfuric acid, from 13 to 25% of sodium sulfate, and from 2 to 15% of zinc sulfate, optionally with 1 to about 5% of ferrous sulfate. The optimum quantity of zinc sulfate for industrial practice appears. to be 3 to 5%; however, 15% zinc sulfate is quite satisfactory for reducing gel swelling and improving yarn properties. With the addition .of amines to the baths, it is possible to obtain excellent yarns in the upper range of bath acidity under which conditions normal, unmodified viscoses give yarns of decreased quality. The temperature range of best spinnability is from 40 C. to 65 C. On the basis of available data, it is desirable to have the bath acidity and temperatures as low as is practical for a given spinning speed in order to get optimum filament structure and yarn properties. Each of the above concentrations should be adjusted to each other and to the composition of the viscose. It is desirable to use as high a total solids content as possible in the coagulating bath to give the highest degree of gel shrinkage and improved stretchability.

The filaments may be given a long travel of 130 to 250 inches in the primary bath by means of a multiple roller setup which gradually applies tension to the traveling filaments and thereby orients them while they are still plastic. The preferred method, however, is to apply a part or all of the stretch beyond the primary bath in a secondary bath or to use a combination of air and hot-bath stretch. The secondary bath may consist simply of water or of dilute (1% to 3%) sulfuric acid, or it may have the same composition as the coagulating bath but at a greater dilution, e. g., onei'ourth of the concentration of the coagulating bath. The temperature of the secondary bath is preferably between 50 C. and 100 C. Stretches of 80% to 100% are preferred for producing high-tenacity yarn and 20% to 30% for textile type yarns. The bobbin process has been used in the example, but it is immaterial whether spinning is by bobbin. bucket, or continuous process. The yarn cake is washed free of acid and salt, then dried under tension. If preferred, it may be twisteror slasher-dried to enable the dry elongation of the finished product to be controlled. When using the two-bath spinning sys tem, the preferred procedure is to draw off the freshly coagulated gel yarn with a feed-wheel speed equal to or less than the jet velocity and to apply all of the stretch between positively driven rollers traveling at different speeds. The thread can be given a travel of 10 to 50 inches in the secondary bath of hot water or dilute bath. As mentioned above, the amount of stretch applied depends on the properties desired for the yarn.

n the basis of available data, it is thought probable that the mechanism by which amine compounds influence the spinning process is through interaction of thegel filament with the zinc sulfate of the coagulating bath on the one hand, and with the sodium trithiocarbonate of the viscose on the other hand. It has not yet been possible to determine whether this eifect on filamentformation is accomplished through (1) buffer action, (2) transient formation of insoluble complexes, which might exercise some control on the porosity of the initial skin which is set up, or (3) other colloidal effects.

The novel and improved yarns obtainable through the process of this invention have substantially improved Wet tenacities and can, in general, be used instead of regular regenerated cellulose fibers for any purpose where the latter are finding applications, more particularly in the textile and tire cord industries.

Any departure from the above description which conforms to the present invention is intended to be included within the scope of the claims.

I claim:

1. A method of producing regenerated cellulosic structures which comprises the step of spinning viscose into an aqueous 4 to 12% sulfuric acid spinning bath containing at least 2% of zinc sulfate and at least 0.2% of a. bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

2. A method of producing regenerated cellulosic structures which comprises the step of spinning viscose into an aqueous 4 to 12% sulfuric acid bath containing from 2% to 15% of zinc sulfate and from 0.2% to 0.5% of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

3. In a method of producing regenerated cellulosic structures by extruding viscose in an aqueous 4 to 12% sulfuric acid bath containing from 2% to 15% zinc sulfate, the step which comprises incorporating in the said bath at least 0.2% by weight of a bath-soluble monoamine which con-. tains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

4. A method of producing regenerated cellulosic structures which comprises the ste s of spinning viscose in an aqueous 4 to 12% sulfuric acid spinning bath containing from 2% to 15% zinc sulfate and at least 0.2% of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms, passing the said structures into a second bath and stretching said structures in the said second bath to an extent of at least 20%.

5. A process of producing regenerated cellulosic structures which comprises extruding vis cose into a coagulating bath comprising an aqueous solution of 4% to 12% sulfuric acid, 13% to 25% sodium sulfate, 2% to 15% zinc sulfate and at least 0.2% of a bath-soluble monoaminewhich contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

6. A process as defined in claim 5 in which the said structures are passed into a second bath and stretching therein to an extent of at least 20%.

'7. An aqueous 4 'to 12% sulfuric acid spinning bath for the spinning of regenerated cellulosic structures from viscose, said bath containing from 2% to 15% zinc sulfate together with at least 0.2% of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

8. An aqueous sulfuric acid bath for the spinning of regenerated cellulosic structures from viscose, said bath containing from 4% to 12% sulfuric acid, 13% to 25% sodium sulfate, 2% to 15% zinc sulfate and at least 0.2% of a bathsoluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

9. An aqueous sulfuric acid bath for the spinning of regenerated cellulosic structures from viscose. said bath containing from 4% to 12% sulfuric acid, 13% to 25% sodium sulfate, 2% to 15% zinc sulfate, 1% to 5% fe1rous sulfate and 0.2% to 0.5% of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

10. A method of producing regenerated cellulosic structures which comprises the step of spinning unripened viscose into an aqueous 4 to 12% sulfuril; acid spinning bath containing at least 1 11 2% of zinc sulfate and at least 0.2% of a bathsoluble monoamine which contains from 4 to carbon atoms and which contains no radical having more than 6 carbon atoms.

11. A method of producing regenerated cellulosic structures which comprises the step of spinning unripened viscose into an aqueous 4 to 12% sulfuric acid bath containing from 2% to of zinc sulfate and from 0.2% to 0.5% of a bathsoluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

12. In a method of producing regenerated cellulosic structures by extruding unripened viscose in an aqueous 4 to 12% sulfuric acid bath containing from 2% to 15% zinc sulfate, the step which comprises incorporating in the said bath at least 0.2% by weight of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

13. A method of producing regenerated cellulosic structures which comprises the steps of spinning unripened viscose in an aqueous 4 to 12% sulfuric acid spinning bath containing from 2% to 15% zinc sulfate and at least 0.2% of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms, passing the said structures into a second bath and stretching said structures in the said second bath' to an extent of at least 14. A process of producing regenerated cellulosic structures which comprises extruding unripened viscose into a coagulating bath comprising an aqueous solution of 4% to 12% sulfuric acid, 13% to sodium sulfate, 2% to 15% zinc sulfate and at least 0.2% of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

15. A process as defined in claim 14 in which the said structures are passed into a second bath and stretching therein to an extent of at least 20%.

16. An aqueous 4 to 12% sulfuric acid spinning bath for the spinning of regenerated cellulosic structures from unripened viscose, said bath containing from 2% to 15% zinc sulfate together with at least 0.2% of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 8 carbon atoms.

17. An aqueous sulfuric acid bath for the spinning of regenerated cellulosic structures from unripened viscose, said bath containing from 4% to 12% sulfuric acid, 13% to 25% sodium sulfate, to 15% zinc sulfate and at least 0.2% of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

18. An aqueous sulfuric acid bath for the spinning of regenerated cellulosic structures from unripened viscose, said bath containing from 4% to 12% sulfuric acid, 13% to 25% sodium sulfate, 2% to 15% zinc sulfate, 1% to 5% ferrous sulfate and 0.2% to 0.5% of a bath-soluble monoamine which contains from 4 to 10 carbon atoms and which contains no radical having more than 6 carbon atoms.

19. A method in accordance with claim 1 in which the said monoamine is n-amylamine.

20. A method in accordance with claim 1 in which the said monoamine is cyclohexylamine.

21. A method in accordance with claim 1 in which the said monoamine is butylmonoethanolamine.

22. A bath in accordance with claim 9 in which the said monoamine is n-amylamine.

23. A bath in accordance with claim 9 in which the said monoamine is cycloheiwlamine.

24. A bath in accordance with claim 9 in which the said monoamine is butylmonoethanolamine.

NORMAN LOUIS COX.

REFERENCES CITED The following references are of record in the Certificate of Correction Patent No. 2,535,045 December 26, 1950 NORMAN LOUIS COX It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 12, for O,2% read 0.2%; line 73, for 8 5-23-4 read 8.5-23-4; line 74, for the word acids read acid; column 4, line 19, for and4w% read and 4%; columns 7 and 8, Table V1, for that portion of the headings to the table reading Gel Swelling Values coagulating Baths Percent 0aNBB0 ZnS0 Modifier Amyl Oyclo hexyl- Dibutyl Triethy] Tributyi amine amine amine amine amine read Gel Swelling Values Ooagulating Baths Percent Amyl- Gyclohexyl- Dibutyl- Triethyl- Tributy].

amine amine amine amine amine and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 5th day of June, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents, 

1. A METHOD OF PRODUCING REGENERATED CELLULOSIC STRUCTURES WHICH COMPRISES THE STEP OF SPINNING VISCOSE INTO AN AQUEOUS 4 TO 12% SULFURIC ACID SPINNING BATH CONTAINING AT LEAST 2% OF ZINC SULFATE AND AT LEAST 0.2% OF A BATH-SOLUBLE MONOAMINE WHICH CONTAINS FROM 4 TO 10 CARBON ATOMS AND WHICH CONTAINS NO RADICAL HAVING MORE THAN 6 CARBON ATOMS. 